JP2001286725A - Method and apparatus for treating exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently perform the treatment of soot and smoke and denitration at the same time. SOLUTION: Exhaust gas is brought into contact with a metal supported ZSM-5 type zeolite catalyst 10 in a reaction column 11 to make soot and nitrogen oxide in the exhaust gas adsorbed by the catalyst to burn the same at the temperature of the gas. As the metal supported on the zeolite catalyst, there is Cu, Mn or Co.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating exhaust gas containing dust, nitrogen oxides (NOx) and the like.

[0002]

2. Description of the Related Art Exhaust gas emitted from an engine such as a diesel engine not only contains soot and the like that cause air pollution, but also contains toxic nitrogen oxides (NOx).
It is included. It is an urgent task to remove this soot in order to prevent air pollution.

[0003] At present, there are several dust collection methods for treating dust, which is a main component of the smoke, as a method of treating the smoke.
Examples of the dust collection method include the following gravity dust collection, centrifugal dust collection, cleaning dust collection, filtration dust collection, and electric dust collection (basic knowledge on the atmosphere (edited by the person in charge of the Air Quality Bureau, Environment Agency).

[0004] Gravity dust collection is a method in which a dust-containing gas is introduced into a sedimentation chamber, the velocity of the particles is reduced, the inertia force of the particles is lost, and the particles sediment naturally by gravity. The particles can be separated into smaller particles as the particle velocity is reduced by the settling chamber. However, in order to reduce the particle velocity, it is necessary to increase the size of the sedimentation chamber.

[0005] Centrifugal dust collection is a method in which a strong centrifugal force field is created instead of gravity to separate and collect dust particles in a gas from an air flow. Since the particles can have a sedimentation velocity several tens or hundreds of times the gravity, they have excellent dust collection performance. Although it has higher performance than the gravity type and is relatively inexpensive as compared with other dust collecting means, it is necessary to use a high quality material for abrasive dust.

[0006] Washing dust collection is a method of colliding or contacting with dust-containing droplets or liquid films to trap particles in washing water, and is generally called a scrubber. Since such means are used in large quantities, sewage treatment facilities are required. Cyclone scrubbers, scrubbers and spray towers perform significantly better for hydrophilic dust and various mist, but have less capacity for dry dust.

[0007] The filtration and dust collection is a method of filtering and collecting dust by passing a dust-containing gas through a filter medium. Various kinds of chemical fibers and natural fibers are used for the filter cloth. In the case of high temperature, a filter cloth against heat such as glass fiber is used. It has a high dust collection rate, such as exhibiting high performance even for dust of 1 micron or less, and is widely used. However, when the water content is high, it is not suitable for sticky particles.

[0008] Electro-dust collection is a method in which an electric charge is given to a dust-containing gas by utilizing corona discharge to electrically collect charged particles. High performance, but high equipment costs.

[0009] Among the above dust collection methods, centrifugal dust collection is the largest in Japan and electric dust collection has the largest total processing capacity in Japan.

[0010]

However, since the dust collection methods listed above physically collect dust (soot) contained in the smoke, the collected dust must be collected and removed and then separately treated. Yes, nitrogen oxides must be removed separately as well. For this reason, the apparatus is required to have a large dust collecting unit and a dust collecting / nitrogen oxide removing unit, which results in an increase in the size of the device.

The present invention has been made in view of such circumstances, and it is possible to perform soot removal and denitration simultaneously and efficiently, and it is possible to reduce the size in the future.
Another object of the present invention is to newly provide an economical exhaust gas treatment method and its apparatus from the viewpoint of maintenance and management.

[0012]

Means for Solving the Problems The invention created as a means for solving the above problems is characterized by the following.

In the first invention, the gas to be treated is brought into contact with a metal-supported ZSM-5 type zeolite (SiO ₂ / Al ₂ O ₃ = 30 to 80) to remove dust and nitrogen oxides from the gas. It is characterized in that the zeolite is adsorbed and removed, and the adsorbed dust is burnt and removed. Here, the metal is supported on the zeolite by an ion exchange method.

By such means, it is possible to simultaneously remove dust and nitrogen oxides contained in exhaust gas under a single reaction system. Moreover, the combustion of the adsorbed dust can be performed at the temperature of the gas to be treated, which is an effective means from the viewpoint of energy efficiency.

In addition to the ZSM-5 type zeolite, β type (SiO ₂ / Al ₂ O ₃ = 22 to 100) is a zeolite having a denitration effect.
and so on. These zeolites contain metal (eg, Pt,
Even if Pd, Ga, Ce, etc. are supported, and the gas to be treated is brought into contact with the gas and burned at an appropriate temperature, it is possible to simultaneously treat the dust and the nitrogen oxide.

According to a second aspect, the metal is Cu, Mn or
It is characterized by being Co.

According to a third aspect of the present invention, there is provided a reaction column to which a gas to be treated is supplied, a method of adsorbing and removing dust and nitrogen oxides from the gas filled in the reaction column, and further removing the adsorbed dust. In an exhaust gas treatment device comprising a zeolite catalyst that is burned and removed under the gas temperature, the zeolite catalyst is a ZSM-5 supporting Cu, Mn, or Co.
It is characterized by being a zeolite type or a support of this zeolite.

Here, the zeolite catalyst has a structure in which the contact surface with soot is made as wide as possible, for example, a zeolite powder is formed into a honeycomb shape, a pellet shape, a metal or ceramic filter, a bead shape, or the like. The zeolite is supported on the entire surface of a ball-shaped or honeycomb-shaped ball-shaped carrier.
The filling amount of the zeolite catalyst is determined by the load of the gas to be treated (nitrogen oxide-containing soot) per unit catalyst surface.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the creation of the present invention, the inventors confirmed the effectiveness of zeolite used as a denitration catalyst as a catalyst for burning and removing dust, which is a main component of soot, An exhaust gas treatment method using the denitration catalyst and having dust removal and denitration functions was studied.

Zeolite is a kind of crystalline aluminosilicate and is a clay mineral, but many can be synthesized. In addition, those having a crystal structure that does not exist in nature have been synthesized. A type, B type, β type, Y type, and ZSM-5 type described later are well known. These are, as their properties,
Since it has pores and has a molecular sieve action and a cation exchange function, it is used as an adsorbent or a catalyst.

The dust combustion test of the zeolite was performed by the following two methods.

The outline of these methods is as follows. In the first method, a mixture of a powdery zeolite catalyst supporting various metals and dust (soot) is packed in a fixed bed gas flow type column, and nitrogen is mixed. A gas composed of oxygen and nitrogen oxides was passed, the temperature of the reaction column was gradually increased to burn the dust, and the combustion gas was analyzed to observe the effect of burning and removing the dust (hereinafter, Test 1). .

In the second method, a zeolite catalyst supporting various metals is formed into a honeycomb shape, and a 28 kW catalyst is used.
Soot was adsorbed at the time of the initial start-up of the diesel diesel generator, and the combustion removal effect of the adsorbed dust at the temperature of the exhaust gas itself was observed (hereinafter, Test 2). (Test 1) Dust and nitrogen oxide removal performance test of zeolite catalyst according to the present invention FIG. 3 (a) is a schematic diagram of a measurement system according to this test,
FIG. 3B is a schematic view of a fixed bed gas flow type reaction column (hereinafter, reaction column) according to the present test.

The reaction column 33 is filled with a mixture of a powdery sample zeolite catalyst and dust (soot), and both ends thereof are fixed with glass wool 33a so that the mixture does not move due to gas flow. (FIG. 3 (b)). Then, a mixed gas containing components of oxygen and nitrogen oxides (NOx) and helium having a concentration similar to that of a gas discharged from a normal fuel combustion facility such as a diesel engine is supplied into the inside of the reaction column 33. . The reaction column 33 is heated at a constant heating rate by the electric furnace 32 with temperature adjustment, and the dust in the column 33 is burned by the sample gas.

Gas chromatograph analyzers 34 and 35 are installed on the secondary side of the reaction column 33, and measure the concentration of carbon dioxide in the gas passing through the zeolite catalyst to measure the combustion temperature. By measuring the nitrogen concentration of this gas, the conversion rate of nitrogen oxides to nitrogen, that is, the denitration performance is measured.

In this test, the sample zeolite catalyst was:
Na-ZSM-5 type or NH ₄ -ZSM-5 type zeolite is used as a main raw material, and metal ions (Cu, Mn
And Co). The metal ions were supported on the zeolite by an ion exchange method.

Table 1 shows the types and compositions of the main raw materials, and Table 2 shows the types of the sample zeolite.

[0028]

[Table 1]

[0029]

[Table 2]

2. Test procedure 1) 0.285 g of sample zeolite catalyst powder and 0.015 dust powder
g, and then packed into a reaction column 33. Both ends of the mixture are pressed with glass wool 33a. Then, the reaction column 33 is set in an electric furnace, and a sample gas composed of 10% of oxygen, 0.1% of carbon monoxide, and 89.9% of helium is supplied into the reaction column 33 at a rate of 50 ml / min.

2) The reaction column 32 is heated by the electric furnace 33 at a temperature rise of 1 ° C./min from room temperature. When the temperature reached 120 ° C., measurement of the concentration of carbon dioxide and nitrogen was started by the gas chromatograph analyzers 34 and 35, until 660 ° C.
Perform this measurement.

3) After completion of the measurement, the combustion temperature is evaluated by graphing the concentration of carbon dioxide and nitrogen on the vertical axis and the temperature on the horizontal axis. 3. Measuring equipment Gas chromatograph analyzer (Shimadzu GC-14B) FIG. 4 is a characteristic diagram showing the state of dust combustion and denitration by the sample zeolite.

The characteristic diagram shows that zeolite 1 (Cu-ZSM-
5), zeolite 2 (Mn-ZSM-5) and zeolite 3 (Co-
The combustion status of dust by ZSM-5) is shown by plotting the combustion temperature on the horizontal axis and the concentrations of carbon dioxide and nitrogen generated at this time on the vertical axis. Here, the upper part shows the carbon dioxide concentration, and the lower part shows the nitrogen concentration.

As shown in the characteristic diagram, when Cu-ZSM-5 is used, combustion of dust starts at 283 ° C., accompanied by generation of carbon dioxide gas. It can be seen that the peak is active. Also, since nitrogen gas is also produced following carbon dioxide,
The denitration occurred at the same time during the combustion of the dust, and the simultaneous removal of the dust and nitric oxide was confirmed. The same is true for zeolite 2
(Mn-ZSM-5) and zeolite 3 (Co-ZSM-5) were also observed.

Further, Table 3 summarizes the results of the combustion start temperature, the combustion peak temperature, the nitrogen emission amount, and the denitration rate obtained in this test. Incidentally, the nitrogen discharge amount was obtained by integrating the graph of FIG. From these results, it can be seen that combustion starts at 300 ° C. or less and the combustion peak is 380 ° C. or less, regardless of which zeolite is used.

[0036]

[Table 3]

(Test 2) Actual load test of honeycomb-shaped zeolite catalyst according to the present invention FIG. 1 is a schematic diagram of a measurement system according to the present test, and FIG.
Fig. 5 is an external view of a honeycomb-shaped zeolite catalyst according to this test, and Figs. 5 (b), 5 (c), and 5 (d) are external views of the zeolite catalyst alone.

The zeolite catalyst 10 is composed of two or more honeycomb-shaped zeolite catalysts alone, and is packed in a reaction column 11 in FIG. The reaction column 11 is a generator (28k
W) Equipped with 12 exhaust paths, and this column 1
A differential pressure gauge and a NOx meter are installed on the primary side and the secondary side.

The zeolite catalyst is composed of three stages, one of which is composed of four zeolite catalysts alone (FIG. 5 (a)). Further, the single piece is 65 mm x 65 mm x 13
It has a rectangular parallelepiped of 0mm, and zeolite 1
(Cu-ZSM-5) is used.

The two kinds of simple substances tested in this test were:
It is shown below.

In the sectional view taken along the line BB in FIG. 5B, the length of each side of the unit vent is 3.4 mm, and the wall thickness is 0.8 mm.
A single zeolite catalyst having a size of 5 mm (30 cells per square inch, hereinafter abbreviated as 30 cpi) (hereinafter referred to as a 30 cell honeycomb).

In the sectional view taken along the line BB in FIG. 5C, the length of each side of the unit vent is 1.9 mm and the wall thickness is 0.5
zeolite catalyst alone (hereinafter, referred to as 100 cell honeycomb) in mm (100 cells per square inch, hereinafter abbreviated as 100 cpi).

Incidentally, the weight of any of the above-mentioned simple substances is about 250 g.
It is. 2. Test procedure 1) Generator (28 kW) 12 with switching valve 15 facing reaction column 11
Is started, and it is operated without load for 20 minutes to adsorb dust to the zeolite catalyst 10.

2) The power generation load is increased to 80%, and the generator 12 is operated for 2 hours in a steady state to burn dust at the exhaust gas temperature.

3) After 2 hours, the load is returned to 0 and the switching valve 15
To the bypass path 16 to stop the generator 12.

In the above procedure, the reaction column during power generation
The exhaust gas temperature, dynamic pressure, static pressure, and NOx concentration are measured at the inlet and outlet of 11. After the test is completed, the used zeolite catalyst 10 is divided vertically, and the dust and the combustion state are observed. 3. Measuring equipment L-type pitot tube NOx-O ₂ analyzer (Shimadzu NOA-307) Test results 1) 30-cell honeycomb Fig. 6 shows the dust adsorption state on the zeolite catalyst (Cu-ZSM-5) alone 20 minutes after start-up (left side) and the zeolite surface after test (CC cross section in Fig. 5). The burning state of the adsorbed dust (right side) is shown. That is, after operating at an actual load of 80%, an exhaust gas temperature of 380 ° C., and 2 hours, the above honeycomb surface (CC
(Cross section) shows the change in the dust burnout situation.

The exhaust gas flow rate during operation was 110 m ³ / h, and the zeolite catalyst (30 cpi, 130 mm × 13
The pressure loss of 0 mm × 390 mm) was 1.568 kPa (160 mmH ₂ O). Further, the reaction column 11 inlet of the NO _X concentration is 681cm ³ / m ³ N (v
ol ppm), the NO _X concentration at the outlet was 644 cm ³ / m ³ N (vol ppm), and denitration with a denitration rate of 5.4% was observed.

2) 100 Cell Honeycomb A 100 cell honeycomb was also measured in the same manner as in the case of the 30 cell honeycomb.

FIG. 7 shows the state of dust adsorption on the zeolite catalyst (Cu-ZCM-5) alone (left) and the surface of the zeolite after the test (CC cross section in FIG. 5) after 20 minutes of startup with a 100-cell honeycomb. The burning state (right side) of the adsorbed dust is shown. This also shows a change in the state of dust burnout on the honeycomb surface (CC cross section) after operation for 2 hours at a load of 80% exhaust gas temperature of 380 ° C.

The flow rate of the exhaust gas during operation was 110 m ³ / h, and the zeolite catalyst (100 cpi, 130 mm × 1
The pressure loss of 30 mm × 390 mm) was 2.058 kPa (210 mmH ₂ O). The NO _X concentration at the inlet of the reaction column was 707 cm ³ / m ³ N
(Vol ppm), NO _X concentration at the outlet is ^{651cm 3 / m 3 N (vol} ppm)
The denitration with a denitration rate of 7.9% was observed.

From the above test results, a 30 cell honeycomb and
In each case of 100-cell honeycomb, the dust adsorbed on the zeolite catalyst supporting copper ions is the exhaust gas temperature.
It was confirmed that it was almost burned down at 380 ° C.

In this test, zeolite 2
And 3, that is, the same effect is obtained by using a ZSM-5 type zeolite catalyst supporting Mn or Co.

As is clear from the above, when a zeolite (ZSM-5 type) having a denitrification function carrying Cu, Mn or Co is brought into contact with the gas to be treated, the temperature of the gas to be treated is reduced. Below, it is possible to simultaneously remove dust and nitrogen oxides contained in the gas. (Embodiment) An embodiment of an exhaust gas treatment method according to the present invention will be described with reference to the drawings.

In the exhaust gas treatment method, as described above, a ZSM-5 type zeolite carrying the metal is used, and the zeolite is brought into contact with the gas to be treated at the temperature of the gas to be treated and burned. Thus, dust and nitrogen oxides contained in the exhaust gas are simultaneously performed.

The exhaust gas treatment apparatus according to the present invention is shown in FIG.
As shown in (b), the reaction column 21 to which the gas to be treated is supplied is filled with the zeolite catalyst 20, and the fuel combustion of a generator or the like for discharging a gas containing dust and nitrogen oxides Installed in the exhaust path of equipment. Reaction column 21
The amount of the zeolite catalyst 20 charged into the catalyst is determined by the load of the gas to be treated (nitrogen oxide-containing soot) per unit catalyst surface.

The zeolite catalyst 20 comprises at least two or more zeolite catalysts 20a. The zeolite catalyst unit 20a has a structure in which the contact surface with soot is as large as possible, that is, the zeolite powder is formed into a honeycomb shape or a pellet shape, or a metal or ceramic filter or bead, as in the above test. It is constituted by supporting zeolite on a ball-shaped carrier having a shape of, a ball, or a honeycomb structure.

According to the above test results, when formed into a honeycomb shape, the vent diameter of the zeolite catalyst unit 20a can be adjusted between 30 and 100 cells according to the dust and nitrogen oxide load. If the dust removal / denitration efficiency of any single unit 20a is significantly reduced, it can be easily replaced with a new single unit.In addition, the amount of the catalyst can be arbitrarily adjusted according to the dust and nitrogen oxide load. (For example, as shown in FIG. 2 (2), the filling of 24 to 40 single substances 20a) is possible, which is also effective from the viewpoint of maintenance.

The main raw material of the zeolite catalyst 20 is one in which Cu, Mn or Co is supported on a ZSM-5 type zeolite. As is clear from the first test 2, the zeolite catalyst can burn off dust at the temperature of the supplied gas itself, so that it is not necessary to apply heat from the outside.

With this configuration, the exhaust gas treatment apparatus according to the present invention increases the contact efficiency between the gas to be treated and the zeolite carrying the metal, and efficiently removes the dust contained in the gas at the temperature of the gas to be treated. Can be burned off.

Furthermore, since the zeolite according to the present invention has a denitration function, denitration and dust removal can be performed simultaneously in a single reaction system. Thereby, the processing time of the gas to be treated (smoke) in the reaction system is shortened, and the apparatus can be simply reduced in size. For this reason, the exhaust gas treatment apparatus according to the present invention can be easily installed as an auxiliary facility of the existing soot treatment apparatus, and also helps to maintain the function of the existing exhaust gas treatment facility and take measures to reduce the function.

The operation of the soot treatment apparatus according to the present invention will be described with reference to FIG.

The gas to be treated discharged from the fuel combustion equipment such as a generator is transferred into the reaction column and the zeolite catalyst 20 is discharged.
Contact with. The gas to be treated supplied into the column 21 passes through the vent of the zeolite catalyst 20 toward the discharge port (the void when the ball-shaped or honeycomb-structured zeolite catalyst is filled). At this time, the zeolite catalyst 20 functions as a filter, and adsorbs dust and nitrogen oxides in the gas on the surface of the catalyst 20. The adsorbed dust is burned off under the temperature of the supplied gas to be treated. The gas that has been subjected to the dust removal and denitration treatment is exhausted to the outside of the system, and is subjected to further advanced treatment if necessary.

[0063]

As described above in detail, according to the exhaust gas treatment method and apparatus of the present invention, the gas to be treated is
If the gas is brought into contact with the metal-supported ZSM-5 type zeolite and further burned at the temperature of the gas to be treated, dust contained in the gas can be efficiently removed.

Since the ZSM-5 type zeolite according to the present invention has a denitration function, denitration and dust removal can be performed simultaneously in a single reaction system. Further, the ZSM zeolite supporting Cu, Mn or Co can further improve the efficiency of removing dust and nitrogen oxides.

From these facts, the time required for treating soot in the reaction system is reduced, and the apparatus can be simplified and downsized. Therefore, the handling as an apparatus is facilitated, which is an economically effective means from the viewpoint of production and maintenance.

Therefore, the exhaust gas treatment method and apparatus according to the present invention can be easily installed as an incidental facility of an existing soot treatment apparatus, and can help maintain the functions of existing exhaust gas treatment facilities and countermeasures against deterioration. Also.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an exhaust gas treatment system according to the present invention.

2A is a schematic view of a zeolite catalyst according to the present invention, and FIG. 2B is an external view of a reaction column in an exhaust gas treatment system according to the present invention.

FIG. 3A is a schematic diagram of a measurement system according to a test 1,
(B) is a schematic diagram of a reaction column according to test 1.

FIG. 4 is a characteristic diagram showing the situation of dust combustion and denitration by a sample zeolite.

5A is an external view of a honeycomb zeolite catalyst according to Test 2, and FIGS. 5B, 5C, and 5D are external views of the zeolite catalyst alone.

FIG. 6 shows a 30-cell honeycomb 20 minutes after startup (FIG. 5 (d) CC
The cross-section) shows how dust (soot) adheres to it (left), and the dust (soot) adsorbed on the same honeycomb after 2 hours (right).

FIG. 7: 100-cell honeycomb 20 minutes after startup (FIG. 5 (d) CC
The cross-section) shows how dust (soot) adheres to it (left), and the dust (soot) adsorbed on the honeycomb two hours later burns out (right).

[Explanation of symbols]

 10,20… Zeolite catalyst 10a, 20a… Zeolite catalyst alone 11,21… Reaction column

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) B01J 29/46 ZAB F01N 3/10 A 4G069 29/48 3/24 E F01N 3/02 321 B01D 53/34 129A 3 / 08 ZAB 3/10 53/36 104B 3/24 F term (reference) 3G090 AA02 AA03 BA01 3G091 AA06 AA18 AB09 AB13 BA13 BA14 GB02W GB09Y 4D002 AA12 AB01 AC10 BA04 BA05 DA21 DA23 DA24 DA45 4D048 AA06 AA14BA28 BA28X BA28X BB02 CA02 CC36 CC38 DA03 DA06 EA04 4D058 JA32 JB03 JB06 MA44 PA14 TA02 TA06 UA01 4G069 AA03 BA07A BA07B BC31A BC31B BC62A BC62B BC67A BC67B CA02 CA03 CA07 CA08 CA13 CA18 DA06 EA19 EB14Z05B EB15A EB15Z EB15A EB15Z EB15Z

Claims (3)

[Claims] 1. A gas to be treated is brought into contact with a metal-supported ZSM-5 type zeolite (SiO ₂ / Al ₂ O ₃ = 30 to 80) to convert dust and nitrogen oxides from the gas into the zeolite. An exhaust gas treatment method comprising: removing by adsorption, and burning and removing the absorbed dust. 2. The supported metal is Cu, Mn or
2. The method for treating an exhaust gas containing nitrogen oxides according to claim 1, wherein the exhaust gas is Co. 3. A reaction column to which a gas to be treated is supplied,
An exhaust gas treatment device comprising a zeolite catalyst packed in the reaction column and adsorbing and removing dust and nitrogen oxides from the gas, and further burning and removing the adsorbed dust at the gas temperature. An exhaust gas treatment apparatus, wherein the zeolite catalyst is a ZSM-5 type zeolite supporting Cu, Mn or Co, or a support of the zeolite.